The Parse-Arguments library uses a
standard set of terminology for representing the tokens which might
appear on a command line.

Figure 16-1. Sample command line.

$ sample-app -v --repeat -n=10 foo.txt -- bar.txt

application name

The application name appears first on the command
line. Under Unix-like systems, the application name is passed
to the program exactly as typed. In particular, it may be the
name of a symlink or include one or more directory
components.

command-line arguments

Everything appearing after the application name is a
command-line argument.

Options are also known as flags and switches. They
control the behavior of the application, and may appear in one
of two forms. Short options always
appear after a single dash, but several of them may be grouped
together (e.g. -tzvf in GNU tar). In Figure 16-1,
-v and -n are both short
options. Long options such as
--repeat consist of entire words and are
always preceded by two dashes.

parameter

Parameters modify the behavior of an option. In
Figure 16-1, the
10 following -n is a
parameter. Note that the equals sign may be surrounded by
white space or omitted entirely where unambiguous.

option terminator

The double dash without an option name is called an
option terminator. Any arguments appearing after the terminator
are automatically regular arguments, even if they begin with a
dash.